Looking trim in tight uniforms, Erik Estrada and Larry Wilcox busted up car- theft rings on "CHiPs" in the '70s and, proving that original plots are hard to come by, they will do it again when they reunite tonight on "CHiPs '99."

Los Angeles motorcycle cops Frank "Ponch" Poncherello (Estrada) and Jon Baker (Wilcox), forever cemented in the collective memory with their thumbs up, have thickened up a little since viewers last saw them on their Kawasakis. Estrada still has that Spackle-white smile and all his hair. "Of course that's my real hair, baby," he said last week from Seattle, where he is performing in "Grease."

The two-hour movie, "CHiPs '99," which will be shown at 8 tonight on the TNT network, was executive-produced by Rick Rosner, who created the original NBC se ries, which ran from 1977 to 1983. (TNT broadcasts the reruns 7-9 a.m. weekdays.)

Estrada sounded weary and in pain. His back had gone out. "My sciatica. I'm on the floor in the hotel room, flat on my back right now," he said, groaning loudly. "Jesus Christ, I have to perform in a couple hours." Fortunately, he plays disc jockey Vince Fontaine, a role that requires little dancing.

Estrada, 49, who played a hothead in "CHiPs" and stayed true to form off the set, has spent the past decade rebuilding his career. Wilcox, 51, who played the dull one, has built three computer companies in addition to producing TV and feature films.

As different as a Harley and a minivan, nowadays the two share a mature appreciation for each other, Wilcox said from New York, where he is promoting the movie and raising venture capital for his companies.

"You've got to be brain-dead not to realize that Erik and I are very different human beings," he said. "Erik is Poncherello. I had to come to just appreciate that. We don't have to have brunch every Sunday."

Estrada, who never got top billing -- and doesn't in the new movie, either -- eclipsed his co-star in popularity early on. In 1981 he walked out on the show when his demand for a cut of the syndication pie was denied. He was replaced by Olympic gold medalist Bruce Jenner, who lasted seven episodes. Estrada came back to millions. He already had a Rolls-Royce, given to him a few years earlier after a motorcycle accident on the show left him seriously injured.

BEHIND-THE-SCENES FRICTION

Wilcox left the show the next year. "There was friction; we had different agents, different deals," he said. "Your picture on the cover instead of his; enormous conflicts of interest. All of it was self-indulgence that crossed the line of illusion and reality."

In the end, Estrada said, "working together 16 hours a day for six years was too much."

Past differences didn't have time to resurface on the set of the new movie, a quickie action flick shot in 17 days. They got along just fine, Wilcox said. "I'm not being a spin doctor here -- we got misty-eyed, we laughed and hugged and had a really good time."

There they are, uniforms snug as ever, zipping down the 405, this time on BMWs. There are car chases. Cars on fire. Cars crashing. A brunette in capris, armed and dangerous, does a Sandra Bullock and commandeers a speeding bus. Ponch is a widower with a young son. Baker, who has been made a captain, is married to a fellow CHP officer. Sergeant Joe Getraer (played again by Robert Pine) is now the CHP commissioner. Judge Judy makes a guest appearance, and some original "CHiPs" cast members, including Bruce Penhall (Cadet Bruce Nelson) and Brodie Greer (Officer Baricza), are also in the cast. Two younger fellows, Paul Korver and David Ramsey, are the new heartthrobs.

That was once Estrada territory. Hugely popular in the late '70s, he disappeared after "CHiPs" went off the air in 1983. The millions disappeared. He had become addicted to painkillers after the motorcycle accident. He tumbled badly in the next years. Drugs, drink, debt, divorce, depression. Virtually unemployable, he took what work he could get: B-movies, foreign commercials; he even shilled for the Psychic Friends Network.

"That was then, this is now," Estrada said. The turnaround came a few years ago when he got the lead in a Mexican soap opera, for which he had to learn Spanish. "Dos Mujeres, Un Camino" ran 400 episodes, the longest-running, highest-rated soap in Latin America.

ESTRADA'S COMEBACK

It brought him back to life. He wrote his autobiography, "My Road From Harlem to Hollywood" (just out in paperback). In addition to doing regional theater work, he hosts "American Adventurer," a syndicated travel-adventure show.

Next year, he ventures into the food business. Chips. Seriously, baby. With his picture on the bag, just like Paul Newman. "Estrada Gourmet Chips are in production now," he said. "Green plantain chips, yucca lemon-chile chips. They have 30 percent less fat than regular potato chips."

He and his third wife, Nanette, whom he credits for his well-being, live in Studio City, where Estrada tends a large flower garden.